Hydraulic vehicle brake system with wheel slip control

ABSTRACT

A hydraulic automotive vehicle brake system with wheel slip control includes at least one non-return valve with a closure member that is lifted from its valve seat during evacuation of the brake system. An elastomeric sealing element is arranged between the closure member and the valve seat member.

BACKGROUND OF THE INVENTION

The present invention relates to a hydraulic automotive vehicle brakesystem with wheel slip control which includes at least one non-returnvalve with a valve seat and a closure member that is lifted from thevalve seat during evacuation of the brake system.

German patent application No. 43 37 133 discloses a hydraulic automotivevehicle brake system with wheel slip control, wherein in each brakecircuit of the anti-lock device and/or traction slip control device atleast one non-return valve is used having a valve seat which is notclosed by the closure member of the non-return valve upon evacuation ofthe brake system. The objective of this provision is that the valve seatis not covered before and during filling of the system when the systemis unpressurized. Thus, a connection exists between the primary circuitand the secondary circuit by way of the open non-return valve, with theresult that the secondary circuit can be evacuated and filled with fluidwithout the need to actuate the normally closed magnetic valve. In thecapacity of a closure member, the non-return valve has a ball without aspring. During pressure increase in the system caused by a brakingoperation, correspondingly great flow forces must act upon thenon-return valve in order that the closure member, configured as a ball,is entrained and urged against the valve seat. In another type ofconstruction of the spherical non-return valve, the ball is pressedagainst its valve seat by the effect of gravitational force. However,these reflections are mainly theoretical so that it is not precluded inpractical operations that the closing movement of the sphericalnon-return valve, which is to be effected by flow forces or bygravitational force, will reliably be provided. Due to the high sealingrequirements placed on the non-return valve (which are comparable withthe sealing requirements of a pressure modulation valve inserted in theoutlet to the wheel brake and closed in the initial position), anabsolutely reliable closure of the non-return valve must be ensured inany case. A leakage-free closing function of metallic spherical closuremembers is, however, not ensured in the prior art.

Therefore, an object of the present invention is to improve upon ahydraulic automotive vehicle brake system with wheel slip control of theabove-mentioned type to such effect that a lowcost, functionallyreliable and especially non-leaking non-return valve is provided bysimple means which, in case of need, automatically permitsself-exhaustion of the low-pressure accumulator and evacuation of thepump suction conduit during the high-vacuum process.

SUMMARY OF THE INVENTION

According to the present invention, these objects are achieved in ahydraulic automotive vehicle brake system of the abovementioned type byan elastomeric sealing element arranged between the closure member andthe valve seat member or by a closure member in the form of a sleeveseal, wherein the valve seat member is provided by an annular area of ablind-end bore in an accommodating member that is in contact with thesleeve seal.

Further features and advantages of the present invention can be seen inthe following by way of the description of several embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings,

FIG. 1 is a hydraulic circuit diagram for an automotive vehicle brakesystem with wheel slip control, showing the construction of thenon-return valve.

FIG. 2 is embodiment of the non-return valve in a coaxial arrangementwith a pressure modulation valve closed in its basic position.

FIG. 3 is, as an alternative of FIG. 2, a separate arrangement of thenon-return valve in a cartridge-type construction in an accommodatingmember.

FIG. 4 is a view of the non-return valve as a sleeve-seal non-returnvalve in a cartridge-type construction, including a self-clinchingattachment.

FIG. 5 is a view of the non-return valve as a sleeve seal valve incartridge-type construction, retained by the pressure modulation valvein positive engagement therewith.

FIG. 6 is a view of the non-return valve, configured as a sleeve-sealnon-return valve, which is attached to the pressure modulation valve.

FIG. 7 is a view of the non-return valve, configured as a spring-loadedseat valve, which is integrated in the pressure modulation valve.

DETAILED DESCRIPTION OF THE DRAWINGS

The embodiment of FIG. 1 shows the hydraulic circuit diagram for ahydraulic automotive vehicle brake system with wheel slip controloperating according to the recirculation principle. A braking pressureconduit 9 connected to a braking pressure generator 12 is branched andleads to two wheel brakes 8. Open pressure modulation valves 11 whichare not energized electromagnetically in the basic position are insertedinto the branch lines of the braking pressure conduit 9. This hydraulicsection of the brake system will be referred to as ‘primary circuit’ inthe following text. Pressure modulation valves 10, closed in their basicposition, are arranged between the pressure modulation valves 11, whichare open in their basic position, and the wheel brakes 8. Valves 10 areconnected to a suction conduit 6 of a pump 7. Connected to the suctionconduit 6 is a bypass line that is connected to the braking pressureconduit 9 and accommodates a non-return valve 5. A closure member 1 ofthe non-return valve 5 is acted upon by a spring 4 in the closingdirection, with the result that the non-return valve 5 permits ahydraulic connection exclusively from the suction conduit 6 to thebraking pressure conduit 9. A low-pressure accumulator 18 is positionedin a bypass line between the point where the non-return valve 5 isinserted in the suction conduit 6 and the pump 7. The hydraulic sectionwhich extends from the pressure modulation valves 10, closed in theirbasic position, to the pump 7 will be termed as ‘secondary circuit’hereinbelow. Pump 7 includes (schematically represented) a suction valveand a pressure valve and is in connection to the braking pressureconduit 9 by way of a subsequent noise-damping device. Constructivedetails of the non-return valve 5 represented in the hydraulic circuitcan be seen in a view of the construction shown in the hydraulic circuitdiagram. In this arrangement, the non-return valve 5 is arranged in ablind-end bore 13 of an accommodating member 14. Accommodating member 14may be configured in a cartridge-type construction as an insert memberwhich is separately attached in a valve block. Alternatively, valve 5can be directly mounted downstream in the accommodating member 14 ofeach pressure modulation valve 10 which is closed in its basic position.The non-return valve 5 includes an elastomeric sealing element 3 betweena preferably metallic closure member 1 and a metallic valve seat member2. Sealing element 3 embraces the closure member 1 like a cap. Also, aspring 4 which is subjected to pressure load is arranged on the closuremember 1 and normally retains the non-return valve 5 in its closed basicposition on the valve seat member 2. The closure member 1 includes a pin15 which is guided with play in a pressure fluid passage bore 16 of avalve seat member 2 that closes the blind-end bore 13. By the action ofspring 4, the bowl-shaped elastomeric sealing element 3 bears with itssealing lip 17 against a disc-shaped sealing surface of the valve seatmember 2 which is attached in the blind-end bore 13 of the accommodatingmember 14 by way of clinching. This is why the secondary circuit in theembodiment shown is considered as an isolated section in the hydraulicsystem, separated by electrically and hydraulically operable valves.Thus, according to the present invention, each brake circuit includes anon-return valve 5 which opens in the direction of the primary circuitin opposition to spring 4, connected to the secondary circuit downstreamof the pressure modulation valves 10 which are normally closed in theirbasic position. During evacuation of the secondary circuit, the closuremember 1 lifts from the valve seat member 2 due to the effect of avacuum source in the primary circuit as soon as the pressure differencebetween the primary and secondary circuits has overcome the relativelyweak spring 4 with an opening pressure of roughly 50 mbar. In the openposition of the closure member 1, the vacuum prevailing in the blind-endbore 13 through a channel can automatically propagate between thesealing lip 17 and the pressure fluid passage bore 16 into the secondarycircuit and permit evacuation of the secondary circuit of roughly 95%.When the evacuation process is completed, the closure member 1, by theaction of spring 4, reliably moves into abutment on the valve seatmember 2 so that, both at the commencement and the end of the hydraulicfilling operation, the primary circuit is completely filled with brakefluid and an unchanged vacuum is effective in the secondary circuit.This condition of the secondary circuit is maintained until brake fluidof the primary circuit flows into the secondary circuit and fills it ina wheel slip control operation due to electromagnetic operation of thepressure modulation valve 10 which is closed in its basic position. Thenormal functions of the brake system, such as the normal brakingoperation without wheel slip and the wheel slip control case, are notinfluenced by the bypass isolated by the non-return valve 5 between thesecondary and primary circuits because the hydraulic pressure is higherin the primary circuit than in the secondary circuit in all cases andthe non-return valve 5 is subjected to the action of spring 4. Apartfrom this single objective of the non-return valve 5, i.e., toautomatically permit the evacuation of the secondary circuit during thehigh-vacuum process on the assembly line at vehicle manufacturers'premises, it is another function of the non-return valve 5 to exhaustthe low-pressure accumulator 18 in the direction of the primary circuit.This eliminates the need for the otherwise usual pump replenishmentcycle to ensure complete exhaustion of the low-pressure accumulator 18before wheel slip control commences. The construction of the non-returnvalve 5 disclosed in the present invention has major advantages over thestate of the art. The advantages include the robustness of theelastomeric sealing element 3 with respect to contaminants in thehydraulic circuit, thereby rendering special filtering provisionsunnecessary. Another advantage is seen in the absolutely reliablesealing of the closure member 1 on the valve seat member 2 which is dueto the use of an elastomeric sealing element (material), on the onehand, and the special design of the sealing element 3 with a sealing lip17, on the other hand. Sealing lip 17 is pressed annularly onto thevalve seat member 2 by the action of spring 4. Additionally, the valveseat member 2 adopts the function of closing the blind-end bore 13 whichcan be achieved especially simply by clinching the valve seat member 2in the accommodating member 14. Not only is an undesirable filling ofthe pressure accumulator 18 with fluid of the primary circuit duringnormal braking operations prevented by the spring, the latter alsorenders possible a partial evacuation of the secondary circuit.

The embodiment of FIG. 2 shows a favorable arrangement of the non-returnvalve 5 inside an accommodating member 14 for the pressure modulationvalves 10, 11. A particularly appropriate installation position for thenon-return valve 5 is the stepped bore 19 in the accommodating member 14of the pressure modulation valve 10 which is closed in its basicposition. This is because the coaxial alignment of the blind-end bore 13at the end of the stepped bore 19 provides a simple manufacture in onemachining operation along with an expedient positioning for thenon-return valve 5 so that the accommodating member 14 is configured inconformity with the demands of automation. The accommodating member 14shown in the FIG. 2 embodiment accommodates the pressure modulationvalves 10, 11 in two parallel valve rows. On the side of the housingbody remote from the stepped bore 19, there is another stepped bore 20in a section which is provided to accommodate an electric motor drivingthe pump. The pump 7 (not shown in FIG. 2) is automatically positionedtransversely to the stepped bores 19, 20 in the accommodating member 14.The accommodating member 14 is also shown in a section along its line ofsymmetry so that the assembly of function groups is identical on theright-hand side of the line of symmetry of the accommodating member 14.

Inasmuch as not all the details of the non-return valve 5 are referredto in FIG. 2, the features shown in the drawings nevertheless correspondto the details of construction of the non-return valve 5 which have beendescribed with respect to the FIG. 1 embodiment.

In addition to the constructive embodiments of the non-return valve 5shown in FIGS. 1 and 2, reference is made to the knub 21 on the sealingelement 3 which ensures that, in the open position of the non-returnvalve 5, a sufficiently large distance is maintained between the endsurface of the blind-end bore 13 and the end surface on the sealingelement 3 in order that the hydraulic pressure of the primary circuitwill act in the sense of closing the non-return valve 5 when brake fluidenters the blind-end bore 13.

FIG. 2 shows a non-return valve 5 for each pair of pressure modulationvalves 10 closed in their basic position. If, however, the hydraulicbrake circuit is modified, it may also be possible to assign onenon-return valve 5 to each pressure modulation valve 10 closed in itsbasic position.

Based on the embodiments of FIGS. 1 and 2, the FIG. 3 embodiment shows anon-return valve 5 which is slipped as a cartridge unit into theblind-end bore 13 for evacuation and filling of the brake system. Thecartridge unit is attached to the bottom end portion of the pressuremodulation valve 10 which is closed in its basic position and alsomanufactured in the cartridge-type construction. The result is apreassembled assembly unit which is adapted to be tested prior to beingmounted into the accommodating member 14. Due to the attachment of thecartridge unit to the pressure modulation valve 10, said's bottom endportion includes a transverse channel which is confined by an annularfilter and extends to the suction-side pressure fluid port of the pump 7by way of the blind-end bore 13. According to FIG. 3, both thenon-return valve 5 and the pressure modulation valve 10 adopt theirclosed basic position. Thus, a connecting channel 23 which is positionedcoaxially between both valve elements in the valve housing andpenetrates the transverse channel 22 is separated both from the pressurefluid port of the wheel brake 8 and from the pressure fluid port of thebraking pressure generator 12. An annular seal 24 seals the cartridgeunit in the blind-end bore 13. With the given constructive features, thecartridge unit can be made especially favorably from plastic materialand, appropriately, also comprises a plastic valve seat member 2. Thus,the cartridge unit is open downwards in the direction of the channelconnected to the braking pressure generator 12 for the accommodation ofthe closure member 1 and the spring 4. The above-mentioned valvecomponents are secured in position in the bowl-shaped cartridge unit bymeans of a supporting plate 25. The hydraulic pressure applied by thebraking pressure generator 12 to the cartridge unit is easily taken upby the bottom surface of the pressure modulation valve 10. Theattachment of the cartridge unit for the non-return valve 5 on thepressure modulation valve 10, which is e.g. made by beading or crimping,generally facilitates the assembly when inserting the valve unit, whichis comprised of the pressure modulation valve 10 and the non-returnvalve 5, into the accommodating member 14.

FIG. 4 shows the above-mentioned valve unit in a disintegratedconstruction, meaning that the cartridge unit of the non-return valve 5,detached from the pressure modulation valve 10, is attached in theblind-end bore 13, for example, by way of a so-called self-clinchingengagement. Further, the non-return valve 5 differs from the previousembodiment by using a sleeve seal 26 instead of previously used seatvalves acted upon by spring force. The advantage is that the need for aseparately positioned spring 4 is eliminated by a correspondingpreloading force of the sealing lip. In the present embodiment, thecartridge unit rather resembles a tapered sealing plug having an annulargroove for accommodating an annular sleeve. By the action of itsinternal stress, the sealing lip of the sleeve is urged against the wallof the blind-end bore 13 which quasi adopts the function of a valve seatmember. For the evacuation and filling of the secondary circuit whichextends downstream of the pressure modulation valve 10 in the directionof the pump 7, the sleeve seal 26 opens in the direction of the channelwhich is connected downstream of the blind-end bore 13 and communicateswith the braking pressure generator 12. The cartridge unit includes achannel 27 which extends up to behind the shoulder of the sleeve seal 26and is connected to the suction side of the pump 7 by way of aninterspace of the two valve units. Preferably, a washer 28 is interposedbetween the sleeve seal 26 and the groove flank confined by the channel27.

A sleeve seal 26 on a cartridge unit for the operation of the non-returnvalve 5 is equally disclosed in FIG. 5. Similar to FIG. 3, the cartridgeunit is supported on the end surface of the pressure modulation valve 10which is directed into the blind-end bore 13. Valve 10 is also caulkedas a cartridge into the accommodating member 14. The cartridge unit hasa radial play in the blind-end bore 13, whereby the radial slot and,thus, the connection between the suction side of the pump 7 and thebraking pressure conduit 9, connected to the braking pressure generator12, is interrupted by the action of the lip preloading force as long asthe secondary circuit of the brake is not evacuated.

The embodiment of FIG. 6 shows the non-return valve 5 shown in FIGS. 4and 5 now in a sleeve-type design integral with the cartridge housing ofthe pressure modulation valve 10. To this end, the cartridge housingincludes an extension for accommodating the sleeve seal 26 which extendswith play in the bottom portion of the blind-end bore 13. As has alreadybeen shown in FIG. 3, the valve unit also has a transverse channel 22 inthe cartridge housing between the pressure modulation valve 10 and thenon-return valve 5. Channel 22 connects the wheel brake 8 to the suctionconduit 6 when the pressure modulation valve 10 is open. The suctionconduit 6 is connected through the sleeve seal 26 to the brakingpressure generator 12 by way of the radial clearance in the blind-endbore 13 during the evacuation process.

The embodiment of FIG. 7 corresponds in many features to the embodimentof FIG. 3 so that only major differences with respect to FIG. 3 will bereferred to hereinbelow. The distinguishing feature is that thecartridge housing of the non-return valve 5 is an integral component ofthe pressure modulation valve 10 which abuts with its sleeve-shapedextension in the blind-end bore 13 by way of a ring seal or byclinching. The illustrated embodiments show all favorable possiblesolutions of the present invention which are appropriate in view of anon-return valve 5 for the evacuation of the secondary circuit of abrake system which is simple and reliable to manufacture and satisfiestest and assembly requirements. Special reference is made to the reducedrisk of contamination of the channels which occurs when clearance fitsare used for the assembly of the cartridge units (both for thenon-return valve assembly unit and for the pressure modulation valve10).

What is claimed is:
 1. Hydraulic automotive vehicle brake system withwheel slip control which includes at least one non-return valve having avalve seat member and a closure member that is lifted from the valveseat member during evacuation of the brake system, a suction conduitconnected to a pump and being in communication with a braking pressureconduit when the closure member of the non-return valve has lifted fromthe valve seat member during evacuation of the brake system, a brakingpressure generator and a wheel brake which are interconnected by way ofthe braking pressure conduit, a pressure modulation valve which, in aclosed position, isolates the wheel brake from the suction conduit andfrom a low-pressure accumulator connected to the suction conduit andfrom the pump, wherein the closure member is provided by a sleeve sealhaving a shoulder, and wherein the valve seat member is provided by theannular area of a blind-end bore in an accommodating member that is incontact with the sleeve seal, wherein the non-return valve is attachedin the blind-end bore as an independent assembly unit in acartridge-type construction, in that the cartridge includes a channelwhich extends until behind the shoulder of the sleeve seal and isconnected to the suction side of the pump by way of an interspacebetween the channel and the pressure modulation valve inserted into theaccommodating bore.